This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The essential, conserved yeast protein Pan1 has numerous partners that act at distinct stages of endocytosis. Consistent with its classification as a "date hub" protein, Pan1 may regulate endocytosis by sequentially binding to early- and late-acting factors. We also speculate that Pan1 plays a key regulatory role in determining the timing of when its various partners join or depart from protein complexes that are functioning at endocytic sites. There is evidence that the phosphorylation state of Pan1 controls its recruitment to endocytic sites and also regulates its interaction with some of these endocytic factors. To further characterize how Pan1 may coordinate endocytosis, we aim to identify Pan1-associated factors that bind Pan1 in a phosphorylation-dependent manner, which may also trap endocytic complexes at particular sub-stages of the process. Through tandem mass spectrometry analysis, we can identify Pan1 associated proteins, and then further characterize the physiological role of each Pan1 partner to increase our understanding of Pan1 function during endocytosis.